The Academy underwent various phases, arbitrarily classified as follows:

(1) the Old Academy, under Plato and his immediate successors as scholarchs, when the philosophic thought there was moral, speculative, and dogmatic,

(2) the Middle Academy, begun by Arcesilaus (316/315–c. 241 bce), who introduced a nondogmatic skepticism,

(3) the New Academy, founded by Carneades (2nd century bce), which ended with the scholarch Antiochus of Ascalon (died 68 bce), who effected a return to the dogmatism of the Old Academy. Thereafter the Academy was a centre of Middle Platonism and Neoplatonism